// Copyright (c) 2021, gottingen group.
// All rights reserved.
// Created by liyinbin lijippy@163.com

#include "abel/random/internal/iostream_state_saver.h"

#include <sstream>
#include <string>

#include "gtest/gtest.h"

namespace {

    using abel::random_internal::make_istream_state_saver;
    using abel::random_internal::make_ostream_state_saver;
    using abel::random_internal::stream_precision_helper;

    template<typename T>
    typename abel::enable_if_t<std::is_integral<T>::value, T>  //
    StreamRoundTrip(T t) {
        std::stringstream ss;
        {
            auto saver = make_ostream_state_saver(ss);
            ss.precision(stream_precision_helper<T>::kPrecision);
            ss << t;
        }
        T result = 0;
        {
            auto saver = make_istream_state_saver(ss);
            ss >> result;
        }
        EXPECT_FALSE(ss.fail())            //
                                                   << ss.str() << " "             //
                                                   << (ss.good() ? "good " : "")  //
                                                   << (ss.bad() ? "bad " : "")    //
                                                   << (ss.eof() ? "eof " : "")    //
                                                   << (ss.fail() ? "fail " : "");

        return result;
    }

    template<typename T>
    typename abel::enable_if_t<std::is_floating_point<T>::value, T>  //
    StreamRoundTrip(T t) {
        std::stringstream ss;
        {
            auto saver = make_ostream_state_saver(ss);
            ss.precision(stream_precision_helper<T>::kPrecision);
            ss << t;
        }
        T result = 0;
        {
            auto saver = make_istream_state_saver(ss);
            result = abel::random_internal::read_floating_point<T>(ss);
        }
        EXPECT_FALSE(ss.fail())            //
                                                   << ss.str() << " "             //
                                                   << (ss.good() ? "good " : "")  //
                                                   << (ss.bad() ? "bad " : "")    //
                                                   << (ss.eof() ? "eof " : "")    //
                                                   << (ss.fail() ? "fail " : "");

        return result;
    }

    TEST(IOStreamStateSaver, BasicSaverState) {
        std::stringstream ss;
        ss.precision(2);
        ss.fill('x');
        ss.flags(std::ios_base::dec | std::ios_base::right);

        {
            auto saver = make_ostream_state_saver(ss);
            ss.precision(10);
            EXPECT_NE('x', ss.fill());
            EXPECT_EQ(10, ss.precision());
            EXPECT_NE(std::ios_base::dec | std::ios_base::right, ss.flags());

            ss << 1.23;
        }

        EXPECT_EQ('x', ss.fill());
        EXPECT_EQ(2, ss.precision());
        EXPECT_EQ(std::ios_base::dec | std::ios_base::right, ss.flags());
    }

    TEST(IOStreamStateSaver, RoundTripInts) {
        const uint64_t kUintValues[] = {
                0,
                1,
                static_cast<uint64_t>(-1),
                2,
                static_cast<uint64_t>(-2),

                1 << 7,
                1 << 8,
                1 << 16,
                1ull << 32,
                1ull << 50,
                1ull << 62,
                1ull << 63,

                (1 << 7) - 1,
                (1 << 8) - 1,
                (1 << 16) - 1,
                (1ull << 32) - 1,
                (1ull << 50) - 1,
                (1ull << 62) - 1,
                (1ull << 63) - 1,

                static_cast<uint64_t>(-(1 << 8)),
                static_cast<uint64_t>(-(1 << 16)),
                static_cast<uint64_t>(-(1ll << 32)),
                static_cast<uint64_t>(-(1ll << 50)),
                static_cast<uint64_t>(-(1ll << 62)),

                static_cast<uint64_t>(-(1 << 8) - 1),
                static_cast<uint64_t>(-(1 << 16) - 1),
                static_cast<uint64_t>(-(1ll << 32) - 1),
                static_cast<uint64_t>(-(1ll << 50) - 1),
                static_cast<uint64_t>(-(1ll << 62) - 1),
        };

        for (const uint64_t u : kUintValues) {
            EXPECT_EQ(u, StreamRoundTrip<uint64_t>(u));

            int64_t x = static_cast<int64_t>(u);
            EXPECT_EQ(x, StreamRoundTrip<int64_t>(x));

            double d = static_cast<double>(x);
            EXPECT_EQ(d, StreamRoundTrip<double>(d));

            float f = d;
            EXPECT_EQ(f, StreamRoundTrip<float>(f));
        }
    }

    TEST(IOStreamStateSaver, RoundTripFloats) {
        static_assert(
                stream_precision_helper<float>::kPrecision >= 9,
                "stream_precision_helper<float>::kPrecision should be at least 9");

        const float kValues[] = {
                1,
                std::nextafter(1.0f, 0.0f),  // 1 - epsilon
                std::nextafter(1.0f, 2.0f),  // 1 + epsilon

                1.0e+1f,
                1.0e-1f,
                1.0e+2f,
                1.0e-2f,
                1.0e+10f,
                1.0e-10f,

                0.00000051110000111311111111f,
                -0.00000051110000111211111111f,

                1.234678912345678912345e+6f,
                1.234678912345678912345e-6f,
                1.234678912345678912345e+30f,
                1.234678912345678912345e-30f,
                1.234678912345678912345e+38f,
                1.0234678912345678912345e-38f,

                // Boundary cases.
                std::numeric_limits<float>::max(),
                std::numeric_limits<float>::lowest(),
                std::numeric_limits<float>::epsilon(),
                std::nextafter(std::numeric_limits<float>::min(),
                               1.0f),               // min + epsilon
                std::numeric_limits<float>::min(),  // smallest normal
                // There are some errors dealing with denorms on apple platforms.
                std::numeric_limits<float>::denorm_min(),  // smallest denorm
                std::numeric_limits<float>::min() / 2,
                std::nextafter(std::numeric_limits<float>::min(),
                               0.0f),  // denorm_max
                std::nextafter(std::numeric_limits<float>::denorm_min(), 1.0f),
        };

        for (const float f : kValues) {
            EXPECT_EQ(f, StreamRoundTrip<float>(f));
            EXPECT_EQ(-f, StreamRoundTrip<float>(-f));

            double d = f;
            EXPECT_EQ(d, StreamRoundTrip<double>(d));
            EXPECT_EQ(-d, StreamRoundTrip<double>(-d));

            // Avoid undefined behavior (overflow/underflow).
            if (f <= static_cast<float>(std::numeric_limits<int64_t>::max()) &&
                f >= static_cast<float>(std::numeric_limits<int64_t>::lowest())) {
                int64_t x = static_cast<int64_t>(f);
                EXPECT_EQ(x, StreamRoundTrip<int64_t>(x));
            }
        }
    }

    TEST(IOStreamStateSaver, RoundTripDoubles) {
        static_assert(
                stream_precision_helper<double>::kPrecision >= 17,
                "stream_precision_helper<double>::kPrecision should be at least 17");

        const double kValues[] = {
                1,
                std::nextafter(1.0, 0.0),  // 1 - epsilon
                std::nextafter(1.0, 2.0),  // 1 + epsilon

                1.0e+1,
                1.0e-1,
                1.0e+2,
                1.0e-2,
                1.0e+10,
                1.0e-10,

                0.00000051110000111311111111,
                -0.00000051110000111211111111,

                1.234678912345678912345e+6,
                1.234678912345678912345e-6,
                1.234678912345678912345e+30,
                1.234678912345678912345e-30,
                1.234678912345678912345e+38,
                1.0234678912345678912345e-38,

                1.0e+100,
                1.0e-100,
                1.234678912345678912345e+308,
                1.0234678912345678912345e-308,
                2.22507385850720138e-308,

                // Boundary cases.
                std::numeric_limits<double>::max(),
                std::numeric_limits<double>::lowest(),
                std::numeric_limits<double>::epsilon(),
                std::nextafter(std::numeric_limits<double>::min(),
                               1.0),                 // min + epsilon
                std::numeric_limits<double>::min(),  // smallest normal
                // There are some errors dealing with denorms on apple platforms.
                std::numeric_limits<double>::denorm_min(),  // smallest denorm
                std::numeric_limits<double>::min() / 2,
                std::nextafter(std::numeric_limits<double>::min(),
                               0.0),  // denorm_max
                std::nextafter(std::numeric_limits<double>::denorm_min(), 1.0f),
        };

        for (const double d : kValues) {
            EXPECT_EQ(d, StreamRoundTrip<double>(d));
            EXPECT_EQ(-d, StreamRoundTrip<double>(-d));

            // Avoid undefined behavior (overflow/underflow).
            if (d <= std::numeric_limits<float>::max() &&
                d >= std::numeric_limits<float>::lowest()) {
                float f = static_cast<float>(d);
                EXPECT_EQ(f, StreamRoundTrip<float>(f));
            }

            // Avoid undefined behavior (overflow/underflow).
            if (d <= static_cast<double>(std::numeric_limits<int64_t>::max()) &&
                d >= static_cast<double>(std::numeric_limits<int64_t>::lowest())) {
                int64_t x = static_cast<int64_t>(d);
                EXPECT_EQ(x, StreamRoundTrip<int64_t>(x));
            }
        }
    }

#if !defined(__EMSCRIPTEN__)
    TEST(IOStreamStateSaver, RoundTripLongDoubles) {
        // Technically, C++ only guarantees that long double is at least as large as a
        // double.  Practically it varies from 64-bits to 128-bits.
        //
        // So it is best to consider long double a best-effort extended precision
        // type.

        static_assert(
                stream_precision_helper<long double>::kPrecision >= 36,
                "stream_precision_helper<long double>::kPrecision should be at least 36");

        using real_type = long double;
        const real_type kValues[] = {
                1,
                std::nextafter(1.0, 0.0),  // 1 - epsilon
                std::nextafter(1.0, 2.0),  // 1 + epsilon

                1.0e+1,
                1.0e-1,
                1.0e+2,
                1.0e-2,
                1.0e+10,
                1.0e-10,

                0.00000051110000111311111111,
                -0.00000051110000111211111111,

                1.2346789123456789123456789123456789e+6,
                1.2346789123456789123456789123456789e-6,
                1.2346789123456789123456789123456789e+30,
                1.2346789123456789123456789123456789e-30,
                1.2346789123456789123456789123456789e+38,
                1.2346789123456789123456789123456789e-38,
                1.2346789123456789123456789123456789e+308,
                1.2346789123456789123456789123456789e-308,

                1.0e+100,
                1.0e-100,
                1.234678912345678912345e+308,
                1.0234678912345678912345e-308,

                // Boundary cases.
                std::numeric_limits<real_type>::max(),
                std::numeric_limits<real_type>::lowest(),
                std::numeric_limits<real_type>::epsilon(),
                std::nextafter(std::numeric_limits<real_type>::min(),
                               real_type(1)),           // min + epsilon
                std::numeric_limits<real_type>::min(),  // smallest normal
                // There are some errors dealing with denorms on apple platforms.
                std::numeric_limits<real_type>::denorm_min(),  // smallest denorm
                std::numeric_limits<real_type>::min() / 2,
                std::nextafter(std::numeric_limits<real_type>::min(),
                               0.0),  // denorm_max
                std::nextafter(std::numeric_limits<real_type>::denorm_min(), 1.0f),
        };

        int index = -1;
        for (const long double dd : kValues) {
            index++;
            EXPECT_EQ(dd, StreamRoundTrip<real_type>(dd)) << index;
            EXPECT_EQ(-dd, StreamRoundTrip<real_type>(-dd)) << index;

            // Avoid undefined behavior (overflow/underflow).
            if (dd <= std::numeric_limits<double>::max() &&
                dd >= std::numeric_limits<double>::lowest()) {
                double d = static_cast<double>(dd);
                EXPECT_EQ(d, StreamRoundTrip<double>(d));
            }

            // Avoid undefined behavior (overflow/underflow).
            if (dd <= std::numeric_limits<int64_t>::max() &&
                dd >= std::numeric_limits<int64_t>::lowest()) {
                int64_t x = static_cast<int64_t>(dd);
                EXPECT_EQ(x, StreamRoundTrip<int64_t>(x));
            }
        }
    }

#endif  // !defined(__EMSCRIPTEN__)

    TEST(StrToDTest, DoubleMin) {
        const char kV[] = "2.22507385850720138e-308";
        char *end;
        double x = std::strtod(kV, &end);
        EXPECT_EQ(std::numeric_limits<double>::min(), x);
        // errno may equal ERANGE.
    }

    TEST(StrToDTest, DoubleDenormMin) {
        const char kV[] = "4.94065645841246544e-324";
        char *end;
        double x = std::strtod(kV, &end);
        EXPECT_EQ(std::numeric_limits<double>::denorm_min(), x);
        // errno may equal ERANGE.
    }

}  // namespace
